1. Field
The following description relates to an apparatus and method for providing a multicast and broadcast service (MBS) in a mobile communication environment, and more particularly, to a method of configuring a broadcast area in which a broadcasting service is provided by a mobile communication system and providing a broadcasting service to a plurality of users present in the configured broadcast area and a system for implementing the method.
2. Description of the Related Art
Description made here merely provides background information on embodiments of the present invention, and does not necessarily constitute related art.
To provide an MBS in various mobile communication systems, standards organizations such as Institute of Electrical and Electronics Engineers (IEEE) 802.16e, IEEE 802.16m, Third Generation Partnership Project (3GPP)/Long Term Evolution (LTE), and Worldwide Interoperability for Microwave Access (WiMAX) Forum are proposing the MBS under the names of MBS, enhanced-MBS (E-MBS), multicast broadcast multimedia service (MBMS), enhanced-MBMS (E-MBMS), multicast broadcast service (MCBCS), and so on. In particular, in IEEE 802.16e or IEEE 802.16m (referred to as IEEE 802.16 below), a plurality of base stations are included in one broadcasting service area, in which an MBS standard in which all the base stations send broadcast content to mobile terminals using the same radio resources is determined as a standard of the broadcasting service area, and the MBS broadcast area is defined as an MBS zone or an E-MBS zone.
Referring to FIG. 1, the MBS zone defined in IEEE 802.16e or IEEE 802.16m corresponds to (a). (a) shows an MBS transmission area consisting of two MBS zones. As shown in (a), the MBS zone defined in IEEE 802.16 has a fixed form. In the case of a fixed MBS zone, all base stations constituting the MBS zone (each of the base stations constituting the MBS zone is referred to as a member base station) transmit an MBS signal using the same resources. Thus, a mobile terminal recovers a received signal using all the MBS signals transmitted by the base stations belonging to the MBS zone, and thus can obtain the macro-diversity effect of improving the reception quality of the signal. On the other hand, the member base stations constituting the MBS zone keep channel resources allocated for an MBS. Thus, when there is no MBS user, only a few users are provided with the MBS, or MBS users are concentrated in a very small area, radio resources are wasted.
To solve this problem of an MBS based on IEEE 802.16, some kinds of research have been carried out. The paper “Location Management Area (LMA)-based MBS Handover in Mobile WiMAX Systems” proposes a method of dividing a fixed MBS zone into a plurality of areas referred to as LMAs, allocating broadcast resources to only an LMA in which an MBS mobile terminal is present, and thereby causing not all base stations but only base stations belonging to the LMA to participate in an MBS and saving radio resources. Configurations of MBS zones in accordance with this method are shown in (b). In this method, the MBS zones are subdivided into fixed MBS zones of smaller size. Like the aforementioned method based on IEEE 802.16, this method still has the problem of resource waste dependent on the number of MBS users and the distribution of the users. A third method is a method proposed in WO2013/005935 that has been submitted as a provisional application by the present inventor. As shown in (c), in this method, some base stations that receive signals of excellent quality from a mobile terminal constitute an MBS zone among base stations in a predetermined area. In this method, only the few base stations selected by the mobile terminal participate in MBS traffic transmission, and the member base stations of the MBS zones are dynamically changed according to a channel state between the mobile terminal and base stations. Such a method of dynamically configuring an MBS zone can remarkably reduce the amount of radio resources allocated for an MBS when MBS users are concentrated in a small area, or there are a small number of MBS users.
However, when the number of users increases, or the distribution of the users becomes wider, almost all base stations participate in the MBS, and the MBS becomes similar to the MBS based on IEEE 802.16e/m. As shown in FIG. 1, this method has a drawback in that it is difficult to manage allocation of a service channel. In other words, in the method based on IEEE 802.16, it is possible to readily configure two service channels using the same amount of radio resources. However, in the dynamic setup method, when the distribution of users who use the same MBS becomes wider, only one channel may be formed in an entire MBS transmission area. As a result, it becomes difficult for a service provider to manage channels.
For this reason, there is a need for a method of maintaining the ease of allocation and management of an MBS channel, which is the advantage of a fixed MBS zone configuration based on IEEE 802.16, and also efficiently using radio resources for an MBS like the LMA method or the dynamic MBS zone setup method taking a case in which there are only a few MBS users, or MBS users are concentrated in a small area into consideration.